The slope-intercept form of the equation of a line is often presented in textbooks as
$$y = mx + b\,,$$
where $m$ is the slope of the line and $b$ is the $y$-intercept. How did $m$ and $b$ become the standard variables used for the slope and $y$-intercept? What should we tell students $m$ and $b$ represent to help them make sense of the roles of $m$ and $b$ in that equation?
I think some students would benefit from knowing the original ideas, or any concrete idea really, behind choosing $m$ and $b$ when they are learning how to interpret the equation $y=mx+b$. Then this equation can "make sense" to them in the same way that the naming of variables helps them to make sense of some common physics equations ($t$ is for time, $v$ is for velocity, $F$ is for Force, etc).